I regularly use oak leaves in some tanks. I have never used IAL so I cannot say if they are more tannin-releasing than oak. I won't spend money on leaves when I can collect them in the back yard every autumn.
I collect oak leaves from the ground (so after they have fallen from the tree, when they are completely dead) and just spread them out on paper towels to dry, then bag them. I have never washed them; don't collect any with bird droppings. Any sort of "sterilization" would kill most of what you want from the leaves. I use mine for display in a couple tanks, and as first food for fry (my pygmy cories grow on this) and continuing food for developing Farlowella.
Oak leaves will tint the water, but I found it takes a lot of them to get this really noticeable. My 10g fry tank with the pygmy cories and Farlowella fry has sometimes been quite amber. I don't notice it much in the other tanks where there are few leaves.
Byron.